Hyper-spectral imaging systems capture images for different electromagnetic spectra. An example hyper-spectral imaging system is a label-independent detection (LID) optical reader. A LID optical reader is used to detect drug binding to a target molecule such as a protein, or changes in living cells as cellular material is displaced in response to a drug. Certain types of LID optical readers measure changes in the refractive index on the surface of a resonant waveguide grating (RWG) biosensor of an array of RWG biosensors. The individual RWG biosensors are located in respective wells of a microplate.
In one type of LID optical reader, the different spectra for the hyper-spectral imaging process are provided by a light source that has a tunable wavelength. The tunable light source sweeps narrowband light over a range of center wavelengths. A digital camera captures the images of the RWG biosensors for the different center wavelengths. The wavelength bandwidth of the narrowband light is typically on the order of 1 nm to 2 nm.
To ensure an accurate RWG biosensor measurement, the center wavelength of the narrowband light must be known to a high degree of resolution. To date, achieving such high resolution has proven to be very expensive. Less costly methods for measuring and maintaining the center wavelength at an accurate value can make LID readers and other hyper-spectral imaging systems commercially more attractive.